Mechanism Analysis Of Nonlinear Photoconductive Semiconductor Switches And Its Applications

Duo to the intrinsic characteristics of the GaAs material, Serai-insulating (SI) GaAs Photoconductive Semiconductor Switches (PCSS' s) have more obvious advantages in the performance of both high power and ultra-fast switching than those PCSS' s made of other materials and then can be widely used in ultrahigh speed electronics, field of high power microwave generation and pulse forming (pulse sources of high power ultra-fast electromagnetism,ultra-wide-band microwave generator). Especially the GaAs PCSS can take on particular phenomena of nonlinear characteristics (also known as lock-on effect or high-gain mode) witch made it be very availability., convenience and f lexibleness. Although the great importance was attached to the device research and application of GaAs PCSS, up to the present, there are no reliable theories that can correctly account for the observed transient characteristics produced by the nonlinear mode. In addition, the breakdown and the degeneration of PCSS' s are serious problems in the applications.In this dissertation the mode of luminous charge domain is perfected ulteriorly by deeply studying the dynamics characteristic of high-fielddomain of the trans-electron device with experiment stability of nonlinear PCSS. First, we think periodicity and weakening surge of the nonlinear waveform is caused by self-excitation of the circuit. The electric field thresholds (Et) and maintenance field (Es) of lock-on are modulated by the AC electric field; the nonlinear waveform became two main modes of trans-electron oscillator, namely delay polar domain mode and quenched dipole domain mode. Second, it is found that the deep energy level play a important role in lock on and time delay. They can dynamically change the distribution of electric field, carriers and current densities in PCSS, caused output current to delay and also strengthen the local electric field enough to satisfy qualification of domain, and then cause avalanche. The time of delay is determined by the time of attaining the qualification of domain. Accordingly the mode of luminous charge domain is a preferable mode to explain the mechanism of nonlinear PCSS.On the basis of experiments of breakdown and reliability of PCSS, the mechanism of carriers propagating is deeply studied, and the breakdown characteristics and degeneration mechanism are analyzed in the theory. Firstly it is shown that the thermal breakdown and electron-trapping breakdown theories are the main reason causing the breakdown of PCSS. The electron-trapping breakdown is the main reason accelerating the thermal breakdown, and the thermal breakdown is the fundamentality factor of the breakdown of PCSS. The main points include: the bias electric field and the charges in the traps are the main reasons to generating hot electrons, the number and the kinetic energy of hot electrons are determinative for damage degree of Ga桝s bands, relaxation degree of Ga桝s network reflects the degree of breakdown, and the number of the detrapping of trapped electrons reflects the degree of restoration. Secondly the major mechanisms ofdegeneration of PCSS are caused by both the filamentary nature of the current in high-gain PCSS damage to the chip of the switch and the charge domain reached the anticathode causes the erosion of metal interface. Finally on this base a novel method is presented for longevity improvement of nonlinear PCSS.